Merge branch 'development' into 'master'

src/main/java/nl/tudelft/submit/config/WebSocketConfig.java

.../java/nl/tudelft/submit/controller/EditionController.java

...delft/submit/dto/view/labracore/SubmitEditionViewDTO.java

src/main/java/nl/tudelft/submit/model/SubmitEdition.java

...nl/tudelft/submit/repository/SubmitEditionRepository.java

src/main/java/nl/tudelft/submit/service/EditionService.java

...n/java/nl/tudelft/submit/service/StudentGroupService.java

src/main/resources/application.template.yaml

src/main/resources/messages.properties

src/main/resources/templates/edition/hide.html

src/main/resources/templates/edition/view.html

...a/nl/tudelft/submit/controller/EditionControllerTest.java

...st/java/nl/tudelft/submit/service/EditionServiceTest.java

...a/nl/tudelft/submit/service/grading/GradeServiceTest.java

src/test/resources/application.yaml